[Milsurplus] Re: Milsurplus Digest, Vol 24, Issue 16

[Roger Basford]

----- Original Message ----- >
> Message: 3
> Date: Mon, 10 Apr 2006 15:55:47 -0700 (PDT)
> From: Michael Tauson <kongomt at yahoo.com>
> Subject: [Milsurplus] FSK the old fashioned way (and other things)
> To: "boatanchors at mailman.qth.net" <boatanchors at mailman.qth.net>,
> "milsurplus at mailman.qth.net" <milsurplus at mailman.qth.net>
> Message-ID: <20060410225547.49105.qmail at web32915.mail.mud.yahoo.com>
> Content-Type: text/plain; charset=iso-8859-1
>
> Many moons ago when time was new and gas cost 16 cents/gal at the pumps, 
> FSK
> was one of the modes in use with what were otherwise pretty much AM
> transmitters.  A Collins 18S-4 is enroute here which is, amazingly enough, 
> an
> AM rig.  CW too, if my numbskull evil twin is right.  Anyway, I'd like to 
> use
> this rig for a channelized CW/RTTY (and, if absolutely necessary, voice 
> despite
> my dislike of microphones) system for use with various nets.
>
> Whwere the problem comes up is that I cannot for the life of me remember 
> how
> the old FSK exciters worked.  The web has been no help and my memory has 
> put up
> the "You ARE kidding, right?" flag to indicate it's not even going to try
> anymore.  A clue or two would be most helpful.
>
> As to other things, does anyone know if a T-594/ARC-38A has been 
> successfully
> modified for LSB and/or to make the channel selection slightly fluid so 
> some
> vernier action is available?
>
> Best regards,
>
> Michael, K3MXO ... waiting for the derisive laughter to start ... *sigh*
>
> __________________________________________________

Hi Michael,

Many years ago, whilst working for a long-defunct British government 
department,  I came across a "cheap and cheerful" method of FSK. This was 
used on old Lease-Lend  RCA ET-4332/4331 transmitters and consisted of a 
small box with a 10X crystal socket on the front, a pair of 10X prongs on 
the back and two binding-posts terminals. This was plugged into the TX 
exciter xtal socket and the required rock plugged into the box. The two 
terminals were hooked to (I think)the 80-0-80V keying line from a TTY at the 
receiving station. There was a facility to adjust how much the keying 
voltage affected the amount the of frequency shift (which varied with 
different rocks) but I think that was all. Now, critically, I never saw 
inside a box but they were definitely "homebrew", so perhaps this might jog 
someone's memory! I think a similar contraption, called a "buzz box", was 
also used on the same TXs for CW over noisy circuits. In this case 
low-voltage (6.3V ac?) was applied across the rock to give a buzzy note, 
good for cutting through the QRN on West Africa circuits, I was told! Sorry 
if this is a bit vague but it's nearly 40 years ago :-))

I've just given up and put my Collins 18S-4 on eBay; I tried to locate a set 
of connectors but no luck and I didn't want to hack it about. A shame, as 
it's nice rig and does do AM & CW as you mention.

73,

Roger Basford, G3VKM - Norfolk, England 



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